Method and apparatus for operating fuel injection devices in internal combustion engines



Sept. 19, 1939.

B. BISCHOF 2,173,811 METHOD AND APPARATUS FOR OPERATING FUEL INJECTION DEVICES IN INTERNAL COMBUSTIONENGINES Filed Jan. 7, 1937 2 Sheets-Sheet 1 N v 29 Z6 13 15 16 25 25 11 i 23 10 I4 21\ 17 a 9 i j 8 22 2 7 1 6 Q fi e-i Invenfar:

Sept. 19, 1939.

B. BISCHOF Filed Jan. '7,

1957 2 Sheets-Sheet 2 14 24 31 40 AWW Z5 2 5 3 35 g .55 34 2 2, 3a IT 41 9/ 1 gAl- 5 lnvemar:

Patented Sept. 19, 1939 MEEHUD APPARATEJ Emit @EERAG FUEL ZINJEGTHQN DEVlIQlEfi m ENTERNAL CiDItmlUSTKGN ENGWIES Eernhmd met-ner, Winterthur, Switaerland Application January l, 193?, Serial No. 1195M In Switzerland .llanuary 16, 1936 11 Cid. but

My invention relates to methods for operating fuel injection devices in internal combustion engines and more particularly to methods of operating such devices provided with an injection passage, a displaceable valve member adapted to control said fuel injection passage, a valve opening chamber bounded by at least one face of said valve member in such a way that when said valve member is displaced so as to open said fuel injection passage the volume of said valve opening chamber is increased, a valve closing chamber bounded by at least one further face of said valve member in such a way that when said valve member is displaced so as to open said fuel injection passage the volume of said valve closing chamber is diminished, and means adapted for keeping said valve member in the position in which it closes said injection passage when the pressure is equal in said valve opening chamber and in said valve closing chamber.

- The main object of myinvention is to improve will be understood that while I have described.

what may beconsidered as a preferable embodiment of my invention, I do not limit myself to.

the precise conditions or proportions herein set forth, as they may be varied by those skilled in the art in accordance with the particular purposes for which they are intended, and the conditions under which they are to be utilized.

Referring to the drawings Fig. 1 shows in ver-.

tical section an injection pump with the injector.

Fig. 2 represents another injection pump with an injector by which pump a preliminary injection of the fuel is obtained before the principal injection. I

In the execution according to Fig. 1, I indicates a pump piston fitting the pump cylinder 2 and adapted to be reciprocated therein by the cm 2 on its inward stroke and by the spring 4 on its outward stroke. The shaft 5 of the cam 3 is driven from the combustion engine. The piston I has a cross-guide 6 engaging grooves I of the pinion 8, so that it may be rotated about its axis by means of said pinion and a rack bar 9 without detriment to its reciprocating movement.

In the pump cylinder 2, the pump piston ll faces the pump chamber it which also comprises a a portion it formed by a recess of the pump piston bounded in the sliding surface of the latter by two control edges ii and it which recess is in open communication with the main portion of the chamber it by means of the longitudinal it groove is. A further control edge i5 is formed by the piston front facing the pressure chamber and disposed obliquely with reference to the pieton axis. The suction conduit H, which comes from the fuel reservoir it, reaches laterally the in longitudinal bore of cylinder 2 at such a level that its opening faces the groove it of the piston when the latter is in the lower dead centre position shown in the drawings. The valve loading conduit iii, the opening of which is controlled by the an the injection pipe l9 and the injection passage formed by the nozzle bores 22 leading to the combustion chamber is controlled by the valve needle 23, the ground stem part 25 of which tightly fits the injector body 24. The valve needle 23 is 35 hydraulically operated,'in the opening sense by the fuel pressure prevailing in the annular space 26 under the; stem part 25, which space is in open communication with the delivery conduit, and in the closing sense by the fuel pressure in the chamw ber 21 as well as by the additional loading force of the spring 28 acting upon the valve needle 23. The loading chamber 21 is connected to the loading conduit l8.

The described apparatus operates according to u the following method:

In the lower dead centre position of the piston l, shown in the dawings, i. e. at the end of the suction period, the loading conduit l8, the loading chamber 21 of the injection valve, the delivery 60 conduit IS, the opening chamber 26, and the suction conduit H are in communication with one another, so that they all are under suction pressure. In the beginning of the stroke of the pump piston intothe pump chamber H, the control edge |2 first closes the opening of the suction conduit l1; when the pump piston then moves further on, the fuel is pressed simultaneously through the delivery conduit l9, into the opening chamber 26 and into the loading chamber 21 of the injection valve; thus a rise in the liquid'pressure acting in both directions upon the valve needle stem 25 is obtained. Then the pump piston also closes the opening of the loading conduit l8 by means of the edge [5, so that the further compression is interrupted in the loading chamber 21 of the injection valve and the compressed fuel which acts in the closing direction upon the member 23 is trapped in the loading chamber 21. Because of the oblique position of the edge I! this happens earlier or later according to the angular position of the piston In the opening chamber 26 the fuel is further compressed, until the pressure therein is suflicient to lift the valve needle 23 against the force exerted by the spring-23 and by the compressed fuel in the chamber 21. In the moment in which the loading conduit I8 is shut off from the. pump chamber l4 the fuel loading force exceeds the opening force on the needle 23 because the tip of the valve needle is not exposed to the pressure in the opening chamber 26, whilst the compressed fuel in the loading chamber 21 acts upon the whole cross section of the stem 25.

As soon as the valve needle 23 is lifted, the injection begins; it takes place without interruption or intermittently according as the supply of the fuel forced by the pump piston I through the delivery conduit I9 is sufficient to maintain the pressure under the needle 23 above the closing pressure or not. The injection is ended by uncovering again the opening of the conduit l3 by the pump piston l by means of the control edge II and by thus causing equalization of the liquid pressures acting on both sides of the valve needle stem 25. This equalization of premure takes place immediately, and the injection valve is closed by the spring 23. Thus, the expansion of the contents of the delivery conduit I! through the injection nozzle 22 after the delivery period of the pump is prevented. As the control edge I5 is oblique and the edge perpendicular with reference to the piston axis, the fuel contained in the loading chamber 21 and acting in closing direction upon the member 23 is kept trapped by the piston during a variable part of its stroke so that the duration of the injection and thereby the injected quantity of fuel may be adjusted. After the end of the injection the pump piston continues its displacement stroke, so that the reduction of speed necessary before the reversalof the piston movement takes place after the injection is ended whilst a sufficient piston speed is maintaining during the injection. After the reversal of the piston movement in the inner dead centre position the loading conduit I3 is again closed by the pump piston for a part of the stroke of the latter. During this part of the stroke the pressure in the opening chamber 26 is lowered through the delivery conduit I! because of the increase of volume of the pump chamber ll. Then a pressure equalization between the opening chamber 26 and the loading chamber 21 of the injection valve takesplace again whenthe opening of the loading conduit I8 is uncovered by the piston edge l5, and by further movement of the piston the pressure is lowered simultaneously in both said chambers 26 and 21. Shortly before the lower dead centre position of piston the opening of the suction conduit 11 is uncovered by the control edge l2 and the fuel can flow from the reservoir l6 into the pump chamber I4, whereupon the described working cycle begins anew.

In the execution according to Figure 2 the injection pump is fitted with a separate suction chamber 3| connected to the fuel reservoir l6 by means of a conduit 32. A suction passage 33 leads from the suction chamber 3| to the cylinder bore at such a level that it is closed in the beginning of the compression stroke of the pump piston by the front edge 34 of the latter. The cylinder bore is also connected to the suction chamber 3| by a restricted passage 35 which meets the cylinder bore at the same level as the loading conduit IS. The pump piston is provided with control edges36, 31 and 38, which are placed in such a way that during the inward stroke in succession they open, close and open again the opening of the loading conduit l8. The passage 35 is opened and closed by the control edges 36 and 31, simultaneously with the opening and closing of conduit l3 by these control edges. The edges 36 and 31 are formed by the recess 39 of the piston, which recess is connected to the main portion of the pump chamber H by the londitudinal groove 40; they run perpendicularly to the piston axis. The edge 38, however, is oblique with reference to the piston axis in that part of the piston circumferq ence where it is provided for controlling the opening of the loading conduit l8. It meets the edge 31 in such a way that the recess 4| is also in communication with the recess 39 and thus also forms a portion of the pump chamber M.

As in Fig. l, the piston I may be rotated by means of a rack 9. The remaining parts of the device also correspond to those parts of the device according to Fig. 1 which have the same reference numbers.

The device according to Fig. 2 operates as follows:

On its movement into the pump chamber M the piston first closes the suction passage 33 and then begins its delivery stroke. During the first step of the latter, the measuring and the displacement of the fuel quantity used for the preliminary injection takes place. In the closed loading chamber 21 of the injection valve the pressure is lower during the preliminary injection than during the principal injection, because during the outward stroke of the piston the pressure has been lowered in the loading chamber 21 before shutting (an the loading conduit l8 from the pump chamber Therefore only a small quantity of fuel is displaced until the fuel in the injection conduit has reached ,the opening pressure of the injection valve and the preliminary injection takes place. The latter is ended, as is the principal injection,

by uncovering the opening of the loading conduit l8 by means of the edge 36 and by thus causing equalization of the liquid pressures acting on both sides of the valve needle stem 25, so that the needle 23 closes the injection passage 22'. Thus, in comparison with known types of pumps a considerably better conformity is obtained between the fuel quantity displaced by the piston and that injected during the preliminary injection, and the accuracy of the measuring of the small preliminary injection quantity by means of the pump piston is thus secured to a suflicient degree. The following step of operation of the pump piston consists in pressing fuel into the chambers '26 and 21, to act on both sides upon the stem part 25 of the valve needle. The quantity of fuel fed in this operation to the loading chamber 21 and therefore the pressure of the compressed fuel at tained therein depends on the pump piston speed, because during the compression a part of the fuel displaced by the piston flows back into the suction chamber 3i, through the restricted passage 35. Due to the throttling effect, the fuel quantity flowing off is larger at small piston speed than at high piston speed, so that in the latter case a higher final pressure in the loading chamber 21 is attained than with slow motion of the piston. This compression operation is ended when the edge 31 closes the opening of the loading conduit It, so that in a further step of piston movement the principal injection takes place through the delivery conduit is in the way above described.

For ending the injection the control edge 38 again opens the communication between the loading conduit i8 and the pump chamber It, so that the liquid pressures on both sides of the needle stem 25 are balanced and the injection valve is again closed by the spring 28. As the edge 3'! is perpendicular and the edge 38 oblique with reference to the piston'axis, the part of the piston stroke during which the injection takes place, and which determines the fuel quantity to be injected during the principal injection, is variable in accordance with the position of the rack 9. The beginning of the injection is constant, its end depends on the angular position of the the piston I. The piston now moves still a little further inwards, then reverses its movement and lowers the pressure in the delivery conduit is after the loading conduit l8 has again been shut off. After the edge 31 has again uncovered the opening of the loading conduit E8 the pressure between both said conduits and the spaces communicating with them is equalized. Until the conduit I8 is closed again by the edge 36 aforther lowering of the pressure in the chambers 2! and 26 takes place. The fuel pressure remaining in the loading chamber 21 determinesthe loading of the valve needle 23 during the preliminary injection. At last, the piston I opens again the suction passage 33 by means of the control edge 34 and permits the fuel to fiow into the pump chamber 14, the delivery conduit l9 and the valve opening chamber 28. I wish it to be understood that I do not desire to be limited to the exact details of construction shown and described, for obvious modifications will occur to a person skilled in the art.

What I claim is:

l. The method of operating the fuel injection valve of 'an internal combustion engine in which the injection valve is operated by a double acting expansible chamber motor having a valve-loading working space, a valve-opening working space, and an injection passage communicating with the latter and controlled by the valve, the valve being biased to close when pressures in said -working spaces approach equalization, which ing working; space, a valve-opening workin space, and aninjection passage communicating with the latter and controlled by the valve, the valve being biased to close when pressures in said working spaces are equalized, which method comprises compressing fuel oil into both working spaces until a substantial pressure is developed in both, then isolating the valve-loading space and continuing compression into the valve-opening space, and finally causing pressure equalization between said spaces; and repeating the above valve operating sequence in time with the cycle of the engine.

3. The method of operating the fuel injection valve of an internal combustion engine in which the injection valve is operated by a double acting expansible chamber motor having a valve-loading working space, a valve-opening working space, and an injection passage communicating with the latter and controlled by the valve, the valve being biased to close when pressures in said working spaces are equalized, which method comprises compressing fuel oil into both working spaces until a substantial pressure is developed in both, then isolating the valve-loading space and continuing compression into the valve-opening space, and finally causing pressure equalization between said spaces; repeating the above valve operating sequence in time with the cycle of the engine, and varying the interval between isolation of the valve-loading space and said final equalization of pressure.

4. The method of operating the fuel injection valve of an internal combustion engine in which the injection valve is operated by a double acting expansible chamber motor having a valve-loading working space, a valve, opening working space, and an injection passage communicating with the latter and controlled by the valve, the valve being biased to close when pressures in said working spaces are equalized, which method comprises compressing oil into the valve-opening space, then causing pressure equalization between said spaces while compressing oil into both, then isolating the valve-loading space while continuing to compress oil into the valve-opening space, and finally causing pressure equalization between said spaces, and repeating the above valve operating sequence in time with the cycle of the engine.

The method of operating the fuel injection valve of an internal combustion engine in which the injection valve is operated by a double acting expansible chamber motor having a valveloading working space, a valve-opening working space, and an injection passage communicating with the latter and controlled by the valve, the valve being biased to close when pressures in said working spaces are equalized, which method comprises compressing oil into the valve-opening space, then causing pressure equalization between said spaces while compressing'oil into both, then isolating the valve loading space while continuing to compress oil into. the valve-opening space, and finally causing pressure equalization between said spaces; repeating the above valve operating sequence in time with the cycle of the engine, and

varying the interval between isolation of the said spaces while compressing oil into both, a slight escape of oil is permitted, so that the pressures developed in the spaces tend to increase with rising speed of operation.

8. The method of operating the fuel injection valve of an internal combustion engine of that type in which liquid fuel fed under hydrostatic pressure to the valve develops in a valve opening working space in communication with the fuel injection passage of the valve an opening force on the valve proportional to said hydrostatic pressure and in which the valve is loaded in a closing direction, which method comprises increasing the loading whereby the valve is held closed, then arresting the increase of the loading force and maintaining the latter while increasing the hydrostatic pressure whereby the valve is caused to open, then lowering the hydrostatic pressure whereby the valve is caused to close and repeating the above valve operating sequence in time with the cycle of the engine.

9. The method of operating a fuel injection valve of an internal combustion engine, in which the injection valve is operated by a double acting expansible chamber motor having a valve loading working space, a valve opening working space, and an injection passage controlled by the valve and in communication with the valve opening working space, the valve being biased to close, which method comprises developing hydrostatic pressures in said valve loading working space and in said valve opening working space at such relative rates that the valve remains closed, then so changing the relative rates of development of hydrostatic pressure that the valve is caused to open and close, finally dissipating the pressure in said working spaces and repeating the above valve operating sequence in time with the cycle of the engine.

10. The method of operating a fuel injection valve of an internal combustion engine, in which the injection'valve is operated by a double acting expansible chamber motor having a valve loading working space, a valve opening working space, and an injection passage controlled by the valve and in communication with the valve openabove valve operating sequence in time with the.

cycle of the engine.

11. The method of operating the fuel injection valve of an internal combustion engine of that type in which liquid fuel fed under hydrostatic pressure to the valve develops in a valve opening working space in communication with the fuel injection passage of the'valve an opening force on the valve proportional to said hydrostatic pressure and in which the valve is loaded in a closing direction, which method comprises increasing the hydrostatic pressure while at least maintaining the loading force whereby the valve is caused to open, then lowering the hydrostatic pressure while at least maintaining the loading force whereby the valve is caused to close, then increasing the loading force whereby the valve is held closed, then arresting the increase of the loading force while increasing the hydrostatic pressure whereby the valve is caused to open again, then lowering the hydrostatic pressure whereby the valve is caused to close, thereafter lowering the loading I force to its initial value; and repeating the above valve operating sequence in time with the cycle 

